1. Field of the Invention
This invention is directed to coating compositions, in particular, to aqueous coating compositions having improved acid etch resistance and mar resistance and good gloss and distinctness of image.
2. Description of the Prior Art
The finishing system of choice presently being used on the exterior of automobiles and trucks comprises a clear coating applied over pigmented base coating that is applied over a primer coating. The clear coating provides protection to the pigmented base coating and improves the appearance of the overall finish, such as, gloss and distinctness of image. The clear coating also is required to have excellent acid etch resistance. Acid etching occurs when the clear coating is exposed to acid rain and other air pollutants. Further, the clear coating is required to have excellent mar resistance to withstand marring caused by commercial car washes or by other cleaning of the exterior surface of a vehicle.
Conventional waterborne clear coatings of polyester crosslinked with melamines or acid polymers crosslinked with epoxy moieties have not been able to provide the level of acid etch resistance and mar resistance that is desired by the automotive and truck industry.
It would be desirable to form a waterborne clear coating composition that provides a protective clear top coat finish that not only has good gloss and distinctness of image that provides an excellent appearance but that also has a high level of acid etch resistance and excellent mar resistance.